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Geo(ogicaf?echnws Inc Page 2 <br /> Groundwater Monitormg Report <br />' Project No 425 2 <br /> • August 12, 1999 <br />' A summary of findings include <br /> I Hydrogeology <br />' • For the past year, the shallow groundwater gradient has moved towards the NE Over <br /> the course of the project the predominate flow is to the N, with slight variation to the <br /> NW and NE _ <br /> • Vertical groundwater gradient does exist at approximately the same slope as the <br /> horizontal gradient At times the site has experienced both a negative and positive <br /> vertical gradient <br /> 2 Groundwater Contamination <br /> Floating product has routinely been detected in MW-2 (located in the area of the <br /> former USTs) during late fall and winter months <br /> t • The contamination observed in MW-102 during 1997 and early 1998 has attenuated <br /> to a large extent However, BTEX compounds are still present <br /> • The contamination observed in MW-202 has decreased from the initial concentration <br /> observed after installation <br /> o The domestic well at 1600 Durham Ferry Road detected trace concentrations of <br /> Benzene <br /> It is recommended that <br />' o Future monitoring should include a complete natural attenuation parameter analysis <br /> o This site should be evaluated for the need of source removal to provide needed protection <br /> to public health and the environment <br /> 10 GROUNDWATER MONITORING <br /> 1 1.1 Hydrology of Site <br />' 1.1.1 Horizontal Groundwater Gradients <br />' Water Table Wells <br /> The average water table elevation at the site was 72 66 feet above mean sea level The water <br /> table groundwater gradient was 0 0017 ft/ft flowing N37E A review of the groundwater <br />' gradients shows that the dominant groundwater flow is in a northern direction with the slope <br /> ranging from 0 0012 up to 0 0289 ft/ft The gradient direction for this event, the November <br /> 13, 1998 and the May 29, 1998 monitoring events were more easterly then has been observed <br />' at the site in the past The cause for this shift is not clear, but all of these wells have been <br /> surveyed into a common plane, so the data should be correct Table I of Appendix A <br /> summarizes the water table groundwater gradients and levels to date <br />'F <br /> �i <br />'1 <br /> tl <br />